The problem of estimating the current signal-to-noise ratio in a radio channel is of timely interest for radio communication systems and consequently has long been a subject of engineering development. There are known methods and devices for estimating the current value of signal-to-noise ratio, described, for instance, in U.S. Pat. Nos. 6,028,894; 6,480,315; 6,717,976; 6,760,370; 7,190,741; 7,414,581; 7,484,136; 7,577,100; 7,729,663; 7,362,801; 7,773,681; 8,194,558; and 8,279,914 and in U.S. Patent Application Publications 2010/0054319; 2011/0188561; 2011/0307767; and 2012/0131415.
Similar technical solutions are presented in Russian Federation Patents 2,332,676; 2,354,981; 2,434,325; 2,446,448 and in Russian Federation patent application 2006129316. U.S. Patent Application Publication No. 2011/0188561 discusses a method and device for estimating the signal-to-noise ratio comprising a demodulator, a decoder of error-correcting codes, and a signal-to-noise ratio estimating unit. The estimate of the current signal-to-noise ratio is based on measuring the signal level and noise level, carried out based on processing the received mixture of signal and noise. However, using this technical solution at small signal-to-noise ratios is difficult. In U.S. Pat. No. 6,760,370, a method for estimating the signal-to-noise ratio that works effectively at low signal-to-noise ratios is described. This method is likewise based on processing the input mixture of signal and noise. The method and device for estimating signal-to-noise ratio, noise power and signal strength, as described in U.S. Pat. No. 7,773,681 and U.S. Patent Application Publication No. 2010/0054319, generate these estimates based on processing the received mixture of signal and noise. A method for determining the signal-to-noise ratio for signals with QAM modulation presented in U.S. Pat. No. 7,363,801 is based on the analysis of statistical characteristics of the complex envelope of the incoming signal. In the device for measuring the signal-to-noise ratio according to U.S. Pat. No. 6,028,894 which comprises an averaging unit and a signal-to-noise ratio estimating unit, measurements are carried out based on processing a signal from a quadrature mixer output. The method for measuring the signal-to-noise ratio featured in U.S. Pat. No. 8,194,558 proposes to estimate the signal-to-noise ratio based on processing of the received signal. Here, the available decoder of error-correcting codes does not take part in estimating the signal-to-noise ratio. Russian Federation Patent No. 2,354,981 describes a method for measuring low signal-to-noise ratios and a device for its implementation. This technical solution comprises narrow-band filtering of the received signal, switching the high-frequency component phase of this signal, extracting the out-of-band components, and determining their power relative to total signal power. A method and device for measuring the signal-to-noise ratio when decoding convolutional codes are also described in Russian Federation Patent Nos. 2,434,325 and 2,446,448 and include a Viterbi decoder, units to estimate current decoding parameters, and a signal-to-noise ratio estimating unit. However, a drawback of the listed technical solutions is that they are only applicable for estimating the signal-to-noise ratio when decoding convolutional codes. The purpose of the claimed solution is to eliminate drawbacks of known technical solutions.